The teenager whose drunk driving trial included a defense witness saying that he was afflicted with "affluenza" is being sought by federal authorities for a probation violation, authorities said.

The U.S. Marshals have issued a wanted poster for Ethan Couch, who police believe has violated the conditions of his probation, and are offering a $5,000 reward in exchange for the 18-year-old's whereabouts.

Ethan Anthony Couch is pictured in an undated photo released by the U.S. Marshals Service on Dec. 18, 2015.

Couch was convicted of four counts of intoxication manslaughter in 2013 but was not sentenced to any jail time; instead he was given 10 years probation -- a punishment considered a mere slap on the wrist by critics, and one that outraged the victims' families.